Geography

Geography - Layers of Earth

Layers of the Earth
The earth’s structure is divided into layers. They can be either categorized into chemical layers or mechanical layers. The chemical layers are the crust, the mantle and the core. The mechanical layers of the earth are the lithosphere, the aesthenosphere, the mesosphere, the outer core and the inner core. About 1% is crust, 30% is core and the rest the mantle. The crust is solid, mantle is viscous, the outer core is liquid and the inner core is solid. The crust is mostly made up of silicon, oxygen and aluminium. The mantle is made up of silicon and magnesium. The core is made up of iron and nickel. Based on mechanical layers of the earth, lithosphere is the topmost layer, and the inner core is the bottom most layer.

Chemical layers of the Earth
• Crust
 It is the outermost layer
 This is 1% of volume of Earth
 Thin part is oceanic crust and thick part is continental crust
 The main elements of earth’s crust are oxygen(about 47%), silicon(about 28%) and aluminium(about 8%). Other elements are iron, magnesium, calcium, potassium, sodium and others
 Major minerals are mica, quartz, feldspar, pyroxene, amphiboles etc.
 Igneous rocks are abundant in the crust. They are formed by solidification of magma or cooling of lava. Main igneous rocks are granite and basalt
 Other rocks found are metamorphic and sedimentary rocks

• Mantle
 It is about 60 Km from the surface of the earth
 It is the widest section of the earth
 It has upper mantle and lower mantle
 It has magma
 Hard rock in the upper mantle and soft rock in the lower mantle

• Core
 It consists of inner core and outer core (check the mechanical layers of the earth)

Mechanical layers of the earth
• Lithosphere
 It comprises of the earth’s crust and top of the mantle
• Asthenosphere
 It is below lithosphere
 It is the ductile region of the upper mantle

• Mesosphere
 It is below asthenosphere
 It is that part of lower mantle which flows easily

• Outer core
 It is about 2900 km from the surface of the earth
 It is in liquid form
 It has iron and nickel

• Inner core
 It is about 5150 Km from the surface of the earth
 It is the hottest layer of the earth
 It has iron and nickel
 It is solid
 Centre of the earth is around 6370 Km from the surface of the earth